If you are facing Error:unknown connection when trying to change network interface in Linux using nmcli. Please follow below steps to troubleshoot it and fix the same.
Checking the Network interface details.
Let's check the available connections.
[root@TechArticles ~]# nmcli connection show NAME UUID TYPE DEVICE enp0s3 b972dea7-b72d-4e48-a838-bda20615e189 ethernet enp0s3 ethernet-enp0s8 e7dd02fc-f36d-48d7-92a8-30f9be275970 ethernet enp0s8 virbr0 cf62a28b-1744-4754-9e28-1c23b7783406 bridge virbr0
As per above connection details lets suppose you want to start the device enp0s8.
Please Note: In your case device name might be different.
Trying to activate the connection
[root@TechArticles ~]# nmcli connection up enp0s8 Error: unknown connection 'enp0s8'. [root@TechArticles ~]#
As you see in above command output, device is available but still getting Error: unknown connection 'enp0s8'.
Basicly getting this error because the command nmcli connection up enp0s8 is looking for a connection NAME: enp0s8to up but there is no connection with NAME: enp0s8 however we do have a connection with NAME: ethernet-enp0s8.
I hope you can now tell the difference between "NAME" and "DEVICE" while seeing the connection listings.
To start the device, please follow the steps provided below.
There are two choices. You can either fix the name or start the device with the UUID.
Activating connection using UUID
Let's try starting the connection using the UUID.
[root@TechArticles ~]# nmcli connection up e7dd02fc-f36d-48d7-92a8-30f9be275970
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/5)
[root@TechArticles ~]# nmcli connection show
NAME UUID TYPE DEVICE
enp0s3 b972dea7-b72d-4e48-a838-bda20615e189 ethernet enp0s3
ethernet-enp0s8 e7dd02fc-f36d-48d7-92a8-30f9be275970 ethernet enp0s8
virbr0 cf62a28b-1744-4754-9e28-1c23b7783406 bridge virbr0
[root@TechArticles ~]# ip address show enp0s8
3: enp0s8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 08:00:27:c2:15:90 brd ff:ff:ff:ff:ff:ff
inet 192.168.111.77/24 brd 192.168.111.255 scope global noprefixroute enp0s8
valid_lft forever preferred_lft forever
inet6 fe80::4705:63f9:c16e:7cb0/64 scope link noprefixroute
valid_lft forever preferred_lft forever
You can see the same connection activated using the UUID and you can see the connection up using the correct connectionNAME : ethernet-enp0s8. Let's see if we can start the interface or not.
Activating connection using connection NAME
[root@TechArticles ~]# nmcli connection up ethernet-enp0s8 Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/6)
As you can see above we are able to start the connection using NAME as well.
We can start the interface sing device by using DEVICE also.
Activating using DEVICE interface
Check the device status by running below command and verify.
[root@TechArticles ~]# nmcli device status DEVICE TYPE STATE CONNECTION enp0s3 ethernet connected enp0s3 virbr0 bridge connected (externally) virbr0 enp0s8 ethernet disconnected -- enp0s9 ethernet disconnected -- lo loopback unmanaged --
To start the device enp0s8 run below command and verify.
[root@TechArticles ~]# nmcli device up enp0s8 Device 'enp0s8' successfully activated with 'e7dd02fc-f36d-48d7-92a8-30f9be275970'. [root@TechArticles ~]# nmcli device status DEVICE TYPE STATE CONNECTION enp0s3 ethernet connected enp0s3 enp0s8 ethernet connected ethernet-enp0s8 virbr0 bridge connected (externally) virbr0 enp0s9 ethernet disconnected -- lo loopback unmanaged --
How to disconnect a interface using nmcli command.
To disconnect the interface by Device use below command.
[root@TechArticles ~]# nmcli device disconnect enp0s8 Device 'enp0s8' successfully disconnected.
How to rename the connection name using nmcli command.
Lets checked the existing device name
[root@TechArticles ~]# nmcli connection show NAME UUID TYPE DEVICE enp0s3 b972dea7-b72d-4e48-a838-bda20615e189 ethernet enp0s3 ethernet-enp0s8 e7dd02fc-f36d-48d7-92a8-30f9be275970 ethernet enp0s8 virbr0 cf62a28b-1744-4754-9e28-1c23b7783406 bridge virbr0
Use below command to rename the connection name
[root@TechArticles ~]# nmcli connection modify ethernet-enp0s8 con-name enp0s8-newname [root@TechArticles ~]# nmcli connection show NAME UUID TYPE DEVICE enp0s8-newname e7dd02fc-f36d-48d7-92a8-30f9be275970 ethernet enp0s8 enp0s3 b972dea7-b72d-4e48-a838-bda20615e189 ethernet enp0s3 virbr0 cf62a28b-1744-4754-9e28-1c23b7783406 bridge virbr0
Above you can see connection name modified from ethernet-enp0s8 to enp0s8-newname
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